The Saturday Play: Murder in ­Samarkand (Radio 4), David Hare's new radio play based on the memoir by Craig Murray, was an arresting 90 minutes. Murray's tale, describing his tumultuous and personally disastrous time as UK ambassador in Uzbekistan, brings with it an urgent plot full of drama, black comedy and terrifying things done by powerful governments to pursue the "war on terror".

But in Hare's taut lines, and especially David Tennant's ­gripping performance as the not-always-likable Murray, this was the sort of radio you just had to sit and listen to until it was over. Right from the start, it all felt entirely credible, especially its dark heart: the British and American governments using torture to source information supporting their legally dubious actions.

Tennant also instantly established Murray as a maverick, passionate and flawed hero; a flamboyant, clever ­outsider wherever he finds himself. Once the play got into its depressing core – Murray fights injustice in ­Uzbekistan and finds he has taken on the political establishment much closer to home – Tennant brilliantly captured a man ensnared and brought down by all his passions. Justice is one of them, but so is cheating on his wife. She tells him how it goes when you take on those with real power: "If you're wining, they ­rewrite the rules."